/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.dx.util;

/**
 * Very simple base class that implements a flag to control the mutability of
 * instances. This class just provides the flag and a utility to check and throw
 * the right exception, but it is up to subclasses to place calls to the checker
 * in all the right places.
 */
public class MutabilityControl {

	/** whether this instance is mutable */
	private boolean mutable;

	/**
	 * Constructs an instance. It is initially mutable.
	 */
	public MutabilityControl() {
		mutable = true;
	}

	/**
	 * Constructs an instance, explicitly indicating the mutability.
	 * 
	 * @param mutable
	 *            {@code true} iff this instance is mutable
	 */
	public MutabilityControl(boolean mutable) {
		this.mutable = mutable;
	}

	/**
	 * Makes this instance immutable.
	 */
	public void setImmutable() {
		mutable = false;
	}

	/**
	 * Checks to see whether or not this instance is immutable. This is the same
	 * as calling {@code !isMutable()}.
	 * 
	 * @return {@code true} iff this instance is immutable
	 */
	public final boolean isImmutable() {
		return !mutable;
	}

	/**
	 * Checks to see whether or not this instance is mutable.
	 * 
	 * @return {@code true} iff this instance is mutable
	 */
	public final boolean isMutable() {
		return mutable;
	}

	/**
	 * Throws {@link MutabilityException} if this instance is immutable.
	 */
	public final void throwIfImmutable() {
		if (!mutable) {
			throw new MutabilityException("immutable instance");
		}
	}

	/**
	 * Throws {@link MutabilityException} if this instance is mutable.
	 */
	public final void throwIfMutable() {
		if (mutable) {
			throw new MutabilityException("mutable instance");
		}
	}
}
